When designing disposable garments for wearing about the lower trunk such as disposable pants, disposable diapers and pant diapers it has become increasingly more important that the articles closely resemble regular underwear in appearance and comfort. For this reason it is necessary for the manufacturers to carefully tailor the articles to optimise fit and comfort. In order to fit snugly around the lower torso, the absorbent articles are provided with elastic elements arranged around contoured leg openings formed by making cut-outs in the garment material.
A major concern when producing disposable garments such as disposable pants, diapers, pant diapers, and the like, is to keep the manufacturing costs as low as possible while providing products with high functionality and an appealing finish. To keep costs at a minimum, high production speeds and little material waste are desirable features of the production method.
The problem of applying elastic elements intermittently and in a nonlinear configuration at the leg edges of an absorbent article has been addressed in U.S. Pat. No. 7,326,311 B2 and in International Patent Application WO 98/25767 A1. The methods disclosed in U.S. Pat. No. 7,326,311 B2 and WO 98/25767 A1 involve making an elastic laminate by attaching a continuous elastic element in a curved pattern on a supporting web and dividing the supporting web in two halves each carrying discrete portions of the elastic element. The two parts of the supporting web are then introduced in a process for longitudinal production of absorbent articles and are attached along the side edges of a production web with the elastic portions forming leg elastic in the finished product.
Although allowing leg elastic to be incorporated in an absorbent article in a fairly simple manner, the methods in U.S. Pat. No. 7,326,311 B2 and WO 98/25767 A1 both require additional material for carrying the elastic element to be introduced in the manufacturing process. As the supporting webs have no function in the finished product but are merely a means for handling the elastic elements in the process, the supporting webs add unwanted cost to the absorbent article and entail excess material consumption which is negative for environmental reasons. When making disposable absorbent articles, the manufacturers are highly concerned to keep the use of materials to a minimum in order to reduce the carbon footprint of the disposable absorbent article.
A common way of forming disposable garments such as pants, diapers and pant diapers is by a cross direction production method where the webs and components forming the garments are moved along a production path parallel with the cross direction of the garments. As the leg edges of a pant-type garment extend generally in the longitudinal direction of the garment transverse to the machine direction, cross-direction production commonly involves applying continuous pre-stretched leg elastic elements along two curvilinear paths extending in the machine direction to form a front half leg elastic and a rear half leg elastic. Continuous application of the elastic elements is preferred, as it allows for higher production speeds than methods involving application of discrete elastic pieces. However, one problem with continuous elastic application in cross direction production is that the leg elastic elements will also extend across the crotch portions of the finished disposable garments. The pre-stretched elastic elements in the crotch portions cause the crotch portion material to contract and deform, giving rise to unwanted corrugations that apart from detracting from the underwear-like appearance of the garment can act as channels in which liquid may flow out of the disposable garment. For these reasons, it is normally preferred if the elasticity in this area can be removed or neutralised.
International Patent Application WO 01/72237 A2 discloses a cross direction type method for applying leg elastic along leg openings in pant type diapers. The method involves adhesively attaching elastic elements in a semicircular pattern along first and second parallel travelling webs having inner edges facing each other. The webs and the elastic elements are then covered by a covering web to form two parallel elastic laminates. The inner edges of the elastic laminates are trimmed off, at the same time removing parts of the elastic elements that would otherwise have extended across the crotch portions of the assembled pant diapers. The two parallel laminates having the leg elastic elements captured between the layers of the laminates are then again covered by a covering web to form a continuous elasticated chassis web that may be further processed into pant diapers by adding waist elastic, absorbent cores, cutting out leg openings, forming side joins, etc.
The method of removing elastic elements from the crotch portions of pant garments as disclosed in WO 01/72237 A2 suffers from the same major drawback as the methods disclosed in U.S. Pat. No. 7,326,311 B2 and WO 98/25767 A1 in that additional material is needed for carrying and supporting the elastic elements in the process.
A further attempt at solving the problem with unwanted elastication in the crotch portion of a disposable pant garment is found in International Patent Application WO 96/23477. The method in WO 96/23477 involves causing the elastic elements to be present in the crotch portion of the produced garments “in a substantially relaxed state”. This is accomplished by severing the elastic elements in the crotch portions, or by applying the stretched elastic in a non-bonded curve and allowing the elastic to relax and assume a non-curved shape.
One disadvantage with the method according to WO 96/23477 is that it may be difficult to synchronize the additional relaxation step to be performed at the correct positions along the production web. Furthermore, as the method requires a separate relaxation step it will complicate the production process with the risk of causing a reduction in speed and an increase in faulty products. A major disadvantage of the method WO 96/23477 is that the end product will still have elastic elements present in the crotch portion of the product. This is highly undesirable both for comfort reasons and for the reason that the elastic elements diminish the undergarment-likeness of the finished disposable pant garment.
WO 96/00551 discloses a diaper produced from a continuous web and having elastic elements that have been deactivated mechanically or by other means such as chemically or by applying heat in areas of the elastic elements crossing the crotch portions of the diapers. The production method in WO 96/00551 suffers from the same problems as the method in WO 96/23477 in that it requires a deactivation step and in that the deactivated elastic elements remain in the crotch portions.
One objective of the present invention is therefore to offer a simplified and more efficient manufacturing method for the production of disposable pant garments. A further object of the invention is to reduce waste of covering materials when producing disposable pant garments. A still further objective is to provide a low-cost yet highly functional, comfortable and selectively elasticated disposable article.